Sexual Deception by Orchids

In most plant-pollinator relationships, the plant is cross-fertilized while the pollinator gains a food reward. In sexually deceptive orchids, the flower mimics a female insect in shape, color, and odor, and males are deceived into "mating" with the flowers, thus transferring pollen without receiving a reward. Schiestl et al. describe an extreme example of this phenomenon in an Australian orchid. The flower produces a volatile compound, 2-ethyl-5-propylcyclohexan-1,3-dione, that is identical in all respects to a pheromone produced by females of its pollinating thynnine wasp. Such dependence on a single compound is highly unusual and may imply limited evolutionary flexibility; nevertheless, the occurrence of more than 300 thynnine-orchid pollination relationships suggests that other highly specific communication systems may occur in nature. F. P. Schiestl, R. Peakall, J. G. Mant, F. Ibarra, C. Schulz, S. Franke, W. Francke, The chemistry of sexual deception in an orchid-wasp pollination system. Science 302, 437-438 (2003). [Abstract] [Full Text]